Line connector for a communications circuit

ABSTRACT

A line protector for a communications circuit comprises a module containing a pair of carbon blocks that provide an air gap in a shunt circuit for grounding high voltage transients. In an overcurrent condition in that shunt circuit, a solder element melts causing contacts in an overcurrent shunt circuit to engage and ground the line. The protector also has an overcurrent responsive mechanism comprising a heat coil for melting the solder element. The heat coil is wound on a bobbin that constitutes one of the contacts in the overcurrent shunt circuit. The bobbin is telescoped with a pin that abuts a cap that engages one of the carbon blocks. The solder element secures the bobbin contact against movement relative to the pin except upon melting of the solder element.

United States Patent [191 [4 1 June 18, 1974 Baumbach LINE CONNECTOR FOR A COMMUNICATIONS CIRCUIT [75] Inventor: Bertram W. Baumbach, Arlington I Heights, 111. [73] Assignee: Reliable Electric Company, Franklin Park, 111.

[22] Filed: Mar. 9, 1973 Appl. No.: 339,928

References Cited UNITED STATES PATENTS 7/1973 Baumbach 317/16 Primary Examiner.lames D. Trammell Attorney, Agent, or Firm-Olson, Trexler, Wolters, Bushnell & Fosse, Ltd.

[5 7] ABSTRACT A line protector for a communications circuit comprises a module containing a pair of carbon blocks that provide an air gap in a shunt circuit for grounding high voltage transients. In an overcurrent condition in that shunt circuit, a solder element melts causing contacts in an overcurrent shunt circuit to engage and ground the line. The protector also has an overcurrent responsive mechanism comprising a heat coil for melting the solder element. The heat coil is wound on a bobbin that constitutes one of the contacts in the overcurrent shunt circuit. The bobbin is telescoped with a pin that abuts a cap that engages one of the carbon blocks. The solder element secures the bobbin contact against movement relative to the pin except upon melting of the solder element.

10 Claims, 5 Drawing Figures 7a /o I6 I" I so 65' 77 7 'um I as; 52? 56 2 I 69 I j 84 I 82 64 72 Q t 70 A 394S 31 52 i e 29 l I 28 I FOR A COMMUNICATIONS LINE CONNECTOR cmcurr CROSS-REFERENCE TO RELATED APPLICATIONS Reference may be had to my copending applications Ser. No. 187,018, filed Oct. 6, 1971 and. Ser. No. 283,492, filed Aug. 24, 1972, now US. Pat. No. 3,743,888.

BACKGROUND OF THE INVENTION SUMMARY AND OBJECTS OF THE INVENTION Typically the protector designed for protection of two lines of a communications circuit. Each circuit is provided with protection against both overvoltage and overcurrent. For this purpose an arrester module is provided for each circuit. When an overvoltage of short duration is applied to either or both of the incoming lines connected to the protector, the protector provides an arc gap path in an overvoltage shunt circuit to ground so that the overvoltage does not reach inside equipment or central office equipment. The are gap is preferably formed by spaced carbon blocks. When an overvoltage fault is of prolonged duration, or an Overcurrent voltage condition is such that there is arcing across the arc gap, the current passing through the overvoltage shunt circuit generates sufficient heat to melt a fusible solder element in the overvoltage shunt circuit. Then the line will be grounded through an overcurrent shunt circuit. In addition, there is a heat coil in the line circuit for supplying heat to melt the solder element in the event of an overcurrent condition that may not cause arcing across the arc gap. In such case the solder element will melt and close the overcurrent shunt circuit to ground.

The module contains normally spaced apart contacts in the form of a cup and a bobbin, both surrounded by an insulating sleeve to prevent possible arc-over between the adjacent module for the other line. These contacts are in the overcurrent shunt circuit. The base of the cup rests on the metallic ground strip and the upper open end of the cup has an intumed flange that provides a region of engagement with a base ordisc portion of the bobbin. The heat coil is wrapped around a shaft on the bobbin whereby heat from the heat coil heats the bobbin which in turn transmits heat to the solder element. A copper cap seats on one end of one of the carbon blocks, and there is a pin that telescopes with the bore of the bobbin shaft and also engages the end wall of the cap for electrical connection therewith. The solder element is within the bobbin bore and secures the bobbin to the pin. The upper end of the bobbin shaft has an insulator with a peripheral metal ring, and the heat coil is connected to the peripheral ring and to the bobbin. The ring and bobbin along with the heat coil are in series with the line. The bobbin and ring are respectively engaged by contact members that connect to line terminal pins of the protector. One of the contact members constitutes a spring that causes the bobbin to move relative to the pin upon melting of the solder element either by the heat coil or by current through the overvoltage shunt circuit.

An object of this invention is to provide a line protector of the type stated in which overvoltage and overcurrent protection are provided, and wherein a heat coil in the line circuit is positioned in surrounding relation to a solder element in the bore of the bobbin shaft such that the solder element can be rapidly melted by sufficient current in the overvoltage shunt circuit or sufficient heat that is generated by the heat coil.

A further object of this invention is to provide a line protector embodying a heat coil, bobbin and pin assembly that is simple and can be mass produced at relatively low cost.

Another object of this invention is to provide a protector of the type stated having a rapid and reliable response to overcurrent faults.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a perspective view of a plug-in type of line protector constructed in accordance with and embodying the present invention;

FIG. 2 is a fragmentary side view in section of the protector;

FIG. 3 is a fragmentary front view in partial section of the protector;

FIG. 4 is an enlarged fragmentary portion of FIG. 3 in the region of the heat coil; and

FIG. 5 is a view similar to FIG. 4 and showing one of the arrester units after melting of the solder element therein.

DETAILED DESCRIPTION Referring now in more detail to the drawing, 10 designates a protector for a pair of communications lines. However, the principles of the invention are applicable to a protector for a single line only. The protector 10 comprises a rectangular base 15 and an elongated detachable housing 16 of generally rectangular crosssection. The base 15 and housing 16 are of a suitable dielectric plastic material. The housing 16 may be secured to the base 15 by bosses 17 which snap into correspondingly shaped openings in the sidewalls of the housing 16. The upper end of the housing 16, namely that remote from the base 15, may have a neck portion 18 terminating in a flange 19 by which the protector may be gripped for removal from and placement into a receptacle.

Mounted in and projecting outwardly from the base 15 is a series of conductive plug-in terminal pins identified by the reference numerals 25-30 inclusive. In the form of the invention shown, there is a first line pin 25, a first central ofiice pin 29, a second line pin 26, a second central office pin 30, a polarizing pin 28, and a ground pin 27. The first line pin 25 and the first central office pin 29 are components in one of the lines through the protector 10 while the second line pin 26 and second central office pin 30 are components in another line through the protector 10. The ground pin 27 is common to both lines while the polarizing pin 28 is an unconnected or dummy" pin that assures proper Orientation of the protector unit when it is plugged into its receptacle.

' 3 The pin 25 is. electrically and mechanically connected to a contact member 35 which is formed of flat spring-like material. As best shown in FIG. 2, the

contact member 35 has a base portion 37 that seats on an elongated rib 38 on the base 15. The base portion 37 has a flange 50 at which the pin 25 is staked. In like manner, contact member 42, which is identical to contact member 35, is connected to the pin 26.

An additional contact member 40 is staked at its bottom flange 39 to the pin 29. Likewise, a contact 4] of a construction similar to that of the contact 40 is staked to the pin 30.

For each of the two lines there is provided a removable and replaceable arrester module 60 for providing a first shunt circuit to the ground pin 27 in the event of an overcurrent condition, and a second shunt circuit to the ground pin in the event of an overvoltage condition. The modules are identical and each includes metallic contacts in the form of a bobbin 62 and cup 64. The upper end of the cup 64 is formed with a somewhat inturned flange 69 that forms a discrete area or region against whichthe cylindrical bobbin disc base 63 may engage in an overcurrent condition, as will hereinafter be described.

The bobbin shaft 65 and disc 63 have an axial bore 67 extending therethrough for receiving a pin 82 of copper or copper alloy that centrally abuts a copper cap 84. The bobbin 62 and pin 82 are thus members that are telescoped together and withthe pin 82 projecting from the bobbin. A fusible solder element 76 is disposed in the bore 67 and bonds the pin 82 to the bobbin 62 so that in the normal operation of the protector, the bobbin and pin members 62, 82 are restrained against relative sliding movement. The solder element 76 preferably surrounds the pin 82.

- The bobbin 62 and, cup 64 are surrounded by an insulating sleeve 66. Within the cup 64 is a carbon arc gap assembly comprising carbon'blocks 68, 70 and an insulating member 72. The carbon block 68 is suitably bonded to the insulating member 72, the latter bearing at one end against the carbon block 70 to constitute a spacer so that an air gap 74 is established between the carbon blocks 68, 70. The air gap 74 is determined by the minimum arc-over voltage for which the unit is designed. The in-turn of the flange 69 is formed by cold working after the blocks 68, 70 and insulation-spacer 72 are inserted into the cup 64. I

It will be seen that the cylindrical cap 84 seats on the I end of the carbon block 68 so as to form a large area of electrical contact therewith. However, the solidified solder element 76 maintains contact-forming bobbin disc 63 spaced from the contact-forming flange 69 while preserving electrical continuity from the bobbin through the pin 82, to the cap 84 and to the block 68.

The upwardly extended parts of the respective contact members 35, 42, 40, 41 lie in grooves 78 formed in sidewalls of the housing 16. Eachof those upwardly extending parts of the contact members 35, 42 terminates in a downwardly extending generally V shaped portion 80 which bears firmly against upper end of the shaft 65 of the associated bobbin 62. Thus, each contact member 35, 42 constitutes a spring tending to urge the bobbin 62 toward the cup 64. However, engagement of the cup 64 and bobbin 62 is prevented, in the normal operation of the protector, by the solder element 76.

The bobbin shaft 65 is diametrally reduced to form a shoulder 71 for supporting a cylindrical insulating member'73. An enveloping metallic contact ring 75 is secured to the periphery of the insulating member 73 for sliding engagement with the cantilever end 77 of the contact 40 or 41, as the case may be. A heat coil of wire 79 is wrapped around the bobbin shaft 65 intermediate the shoulder 71 and disc 63 and with the ends of the heat coil 79 being soldered to the peripheral part of the disc 63 and to the ring 75.

In the normal operating condition of the protector,

current flows in a line circuit running. from pin 29,

through contact member 40, ring 75, heat coil'79, bobbin 62, contact member 35 and to pin 25. In the other line circuit from pin 26 to pin 30 the current flow is through contact members 41, 42, and the heat coil, bobbin and contact ring of the associated module 60.

A grounding strip has a depending leg 48 that is staked to the ground pin 27. The bottoms of the respec-.

tive cups 64 rest upon the grounding strip 45 whereby the cups 64 are grounded. On opposite sides of the leg 48 the grounding strip 45 has thin dielectric tape strips 52, 52 which are downwardly presented and are against the base portions of the contacts 35, 42. The tape strips 52, 52 insulate thecups 54 from the contact members 35, 42.

When an overvoltage condition of relatively short duration is applied to one of the lines, for example at pin 25, the contact 35 provides a conductive path through its upper .V shaped end 80, through bobbin 62, solder element 76, pin 82, cap 84 and to carbon block 68. If the overvoltage is at pin 29, the contact member 40 provides the conductive path through the heat coil 79 to the bobbin 62. This overvoltage transient will arc across gap 74 to carbon block 70 and will be grounded through the grounding strip 45 to the ground pin 27. Under such conditions the solder element 76 does not melt. The components of the protector remain in the condition shown for instance in FIG. 2,'and nothing need be done to restore the protector to its normal operating condition. Similarly, if an overvoltage condition appears on the other line, namely the line in which pins 26 and 30 are located, the ground is through the contact 41 or 42 and the module 60 associated therewith, in the manner previously described.

An overcurrent condition may appear in one of the lines due to a prolonged voltage that is above arcing voltage. Assuming that such overcurrent condition appears on the line containing pin 25 and pin 29 the current through the associated module 60 will cause the solder element 76 to melt, as shown in FIG. 5, since the solder element is in the overvoltage shunt circuit. When the solder element 76 melts, the spring force applied by the contact 35 moves the bobbin 62, heat coil 79 and insulator 73 as a unit relative to the cap 84 and pin 82 while maintaining the contact member 35 against the bobbin shaft end and maintaining the cantilever end 77 of the contact member 40 against the ring 75. This spring force causes the bobbin disc 63 to engage the flange 69 of the cup 64 whereby a metallic ground connection to the ground pin 27 is made through grounding strip 45. The base of the cup 64 is pressed firmly against the grounding strip 45 by reason of the spring pressure from the contact 35 so as to insure a low resistance flow path for the current. If an overcurrent condition as aforesaid, appears in the line containing the pins 26, 30, a ground connection through to the pin 27 will result in the manner just described, except that the ground will be through contact member 41 or 42 and the corresponding parts in the associated arrester module 60.

It should also be noted that the solder element 76 is relatively small and is surrounded by the heat coil 79. In fact, the amount of solder need be only enough to maintain the bobbin and pin 82 firmly soldered together. Accordingly, the solder element melts very quickly due to an overcurrent condition whereby the unit has a rapid response to overcurrent line faults. Furthermore, the in-turned flange 69 provides a reliable contact even if. the unit should be subject to some vibration.

If desired, the plastic strips 52 may be of a type that will melt if sufficient heat is transmitted thereto from the carbon block 70 through the cup 64. This may occur in some kinds of overcurrent conditions, for instance where there is sufficient voltage for arc-over but the current is insufficient to melt the solder pellet. Melting of the plastic strip 52 results in a short metallic path to ground from the contact member 35 or 42, as the case may be, and the spring pressure of the contact member 35 or 42 will push the resilient strip 45 against the base portion 37 of the contact member.

Overcurrent protection is also afforded by the heat coil 79 that is in each module 60 and hence in each line circuit. The operation of the heat coil for each line circuit is the same and so it will suffice to describe such operation for one line circuit, for instance the circuit with pins 25 and 29.

The heat coil 79 is designed to produce sufficient heat to melt the solder element 76 when a predetermined amount of current in magnitude and/or duration flows through the line circuit. This current may appear in the line circuit even though the voltage produced at the arc gap is insufficient for arc-over, and such current may, without protection therefrom, damage equipment in the line. Accordingly, when such overcurrent condition heats the wire of the heat coil 79, the heat is transmitted to the bobbin 62 and thus to the solder element 76 that is surrounded by the heat coil. The solder element 76 becomes flowable and allows the bobbin to slide relative to the pin 82. Thereafter, the spring pressure from contact member 35 pushes the bobbin disc 63 against the upper edge 69 of the cup 64 to complete the overcurrent shunt circuit to the gounding strip 45 and to the ground pin 27.

The protector can be restored to normal operation by removing the housing 16 and then removing the affected module 60. The module 60 may be disassembled and the heat coil assembly replaced. Such heat coil assembly comprises the heat coil 79, bobbin 62, and insulating member 73 with ring 75 along with the pin 82 secured to the bobbin by the solder element 76.

The invention is claimed as follows:

1. A line protector for a communications circuit, said protector having line terminals and a line circuit connected therebetween, a ground terminal, a first normally open shunt circuit from said line circuit to said ground terminal, said first shunt circuit having contacts, spring means biasing said contacts toward each other, a solder element normally maintaining said contacts apart in opposition to said spring means, and a second shunt circuit from said line circuit to ground, said second shunt circuit including blocks forming an are gap, said solder element being in series with said blocks, whereby an overvoltage of' short duration in said second shunt circuit produces an arc at said gap without melting of said solder element and an overvoltage condition of longer duration also produces said are and causes said solder element to melt and close said contacts, said line circuit including means responsive to an overcurrent condition therein and in close proximity to said solder element for melting said solder element, whereby an overcurrent condition in either said line circuit or said second shunt circuit closes said first shunt circuit, said last-mentioned means further includ ing telescoping members, and said solder element being between said telescoping members and restraining relative movement between said telescoping members except upon melting of said solder element.

2. A line protector according to claim 1 in which said last-mentioned means also-comprises a coil of wire in series with the line terminals for generating heat in response to said overcurrent condition through said line terminal, and one of said telescoping members is a metallic member around which the coil is wrapped for transmitting heat to the solder element.

3. A line protector according to claim 2 in which another of said telescoping members is in electrical contact with one of said blocks forming said are gap.

4. A line protector according to claim 2 in which said one telescoping member also comprises one of said contacts in said first shunt circuit.

5. A line protector according to claim 4 in which another of said contacts in the first shunt circuit comprises a cup that receives said blocks, said cup having an open end that is in-turned to provide a region of engagement with said one telescoping member when first shunt circuit is closed.

6. A line protector according to claim 1 in which one of said telescoping members is a pin, another of said telescoping members has a bore that receives said pin, and said solder element is in said bore.

7. A line protector according to claim 3 in which said one telescoping member has a bore, said other telescoping member is in said bore, and said solder element is in said bore.

8. in a line protector for a communications circuit that includes contacts, a solder element normally maintaining said contacts spaced apart, spring means urging said contacts together in opposition to said solder element, one of said contacts comprising .a metallic member, a coil of wire wrapped around said metallic member for generating heat to melt said solder element in a line overcurrent condition, an insulating member on said metallic member, and conductive means on said insulating member, said coil being in series with said metallic member and said conductive means; an improvement including an additional metallic member in relative sliding engagement with said first-mentioned metallic member, said solder element bonding the two members in rigid assembled relationship and normally preventing movement of the first-mentioned member relative to said additional member but permitting such movement upon melting of said solder element, thereby to cause the first-mentioned member to engage the other contact.

9. In a line protector according to claim 8, said firstmentioned member having a bore, said additional member being in said bore, and said solder element also being in said bore.

l 10. In a line protector that has terminals for connection to a line; an overcurrent responsive mechanism in series with the line terminals, said mechanism including a contact, means forming asecond contact, and a tern minal connected to said second contact and adapted for connection to ground, said mechanism including fusible means normally maintaining said contacts separated but operable to close said contacts upon there being an overcurrent condition-of predetermined magrent condition. 

1. A line protector for a communications circuit, said protector having line terminals and a line circuit connected therebetween, a ground terminal, a first normally open shunt circuit from said line circuit to said ground terminal, said first shunt circuit having contacts, spring means biasing said contacts toward each other, a solder element normally maintaining said contacts apart in opposition to said spring means, and a second shunt circuit from said line circuit to ground, said second shunt circuit including blocks forming an arc gap, said solder element being in series with said blocks, whereby an overvoltage of short duration in said second shunt circuit produces an arc at said gap without melting of said solder element and an overvoltage condition of longer duration also produces said arc and causes said solder element to melt and close said contacts, said line circuit including means responsive to an overcurrent condition therein and in close proximity to said solder element for melting said solder element, whereby an overcurrent condition in either said line circuit or said second shunt circuit closes said first shunt circuit, said last-mentioned means further including telescoping members, and said solder element being between said telescoping members and restraining relative movement between said telescoping members except upon melting of said solder element.
 2. A line protector according to claim 1 in which said last-mentioned means also comprises a coil of wire in series with the line terminals for generating heat in response to said overcurrent condition through said line terminal, and one of said telescoping members is a metallic member around which the coil is wrapped for transmitting heat to the solder element.
 3. A line protector according to claim 2 in which another of said telescoping members is in electrical contact with one of said blocks forming said arc gap.
 4. A line protector according to claim 2 in which said one telescoping member also comprises one of said contacts in said first shunt circuit.
 5. A line protector according to claim 4 in which another of said contacts in the first shunt circuit comprises a cup that receives said blocks, said cup having an open end that is in-turned to provide a region of engagement with said one telescoping member when first shunt circuit is closed.
 6. A line protector according to claim 1 in which one of said telescoping members is a pin, another of said telescoping members has a bore that receives said pin, and said solder element is in said bore.
 7. A line protector according to claim 3 In which said one telescoping member has a bore, said other telescoping member is in said bore, and said solder element is in said bore.
 8. In a line protector for a communications circuit that includes contacts, a solder element normally maintaining said contacts spaced apart, spring means urging said contacts together in opposition to said solder element, one of said contacts comprising a metallic member, a coil of wire wrapped around said metallic member for generating heat to melt said solder element in a line overcurrent condition, an insulating member on said metallic member, and conductive means on said insulating member, said coil being in series with said metallic member and said conductive means; an improvement including an additional metallic member in relative sliding engagement with said first-mentioned metallic member, said solder element bonding the two members in rigid assembled relationship and normally preventing movement of the first-mentioned member relative to said additional member but permitting such movement upon melting of said solder element, thereby to cause the first-mentioned member to engage the other contact.
 9. In a line protector according to claim 8, said first-mentioned member having a bore, said additional member being in said bore, and said solder element also being in said bore.
 10. In a line protector that has terminals for connection to a line; an overcurrent responsive mechanism in series with the line terminals, said mechanism including a contact, means forming a second contact, and a terminal connected to said second contact and adapted for connection to ground, said mechanism including fusible means normally maintaining said contacts separated but operable to close said contacts upon there being an overcurrent condition of predetermined magnitude flowing between said line terminals, said mechanism further having a member in relative sliding engagement with the means forming said second contact, said fusible means being between said member and said second contact-forming means and preventing movement of said second contact-forming means relative to said member except upon occurrence of said overcurrent condition. 